INSECTS AND PLANTS 67 



for apple trees, oaks, willows, and elms. The eggs, each of 

 the size of a pin's head, are laid in masses of about six 

 hundred, during July and August. Each cream-coloured 

 egg-mass is covered by yellowish hairs from the abdomen 

 of the female, and has the appearance of a piece of sponge. 

 The caterpillars emerge in May, and, at first, are salmon- 

 coloured, becoming darker as they grow older ; when full- 

 grown they are soot-coloured, and their heads are con- 

 spicuously marked with yellow. On their backs are a 

 double row of blue spots and a double row of red ones, and 

 from these spots arise greyish and yellowish hairs. In 

 July, by which time the caterpillars are fully developed, 

 they spin a silken cocoon, within which they change into 

 chocolate-coloured pupae. Towards the end of July and the 

 beginning of August the moths emerge, and the two sexes 

 are so dissimilar that they would never be taken for the 

 same species by the unentoinological. The male, about 

 thirty-eight millimetres long, is of a general brownish 

 colour, the darker brown upper wings being marked with 

 still darker brown and black, whilst the lower wings are 

 paler brown and unmarked. Owing to its peculiar jerky 

 flight, the male has received the popular name of "zig- 

 zag." The female (fig. 12) is nearly twice the size of her 

 partner, being about sixty-two millimetres long ; in general 

 colour she is creamy white, and the upper wings are 

 marked with sinuous brown lines. Possessed of a large 

 and heavy abdomen, the female is unable to fly, her aerial 

 locomotion being limited to a few struggling flaps which 

 serve to break her fall when she finds herself, probably 

 accidentally, falling to the earth from one of the upper 

 tree branches where she first came into the world. Flight 

 is not the only function denied to the females, for they are 

 unable to eat, and after laying their quota of eggs they die. 

 The American naturalists have, not unnaturally, been 

 somewhat puzzled to account for the rapid spread of the 

 gipsy moth, since its introduction into their country. 



